Development N17 Flashcards
NS deals with a ________ environment
predictable
Genetic determinants
most of the NS circuitry is established prenatally
To deal with variations in habits, social environment, and physical attributes
the CNS maintains the ability to modify its connections, called adaptive adjustments
Sensitive (critical) period
a period during which the capacity to adjust the NS circuitry in response to environment becomes limited
A range of functional properties exist that a circuit could adopt, but if the appropriate experiences are not gained
circuits never attain the ability to process information in a typical fashion (impaired perception and behavior my be permanent)
Experience shapes the visual cortex
depriving visual stimuli, results in cortical blindness, meaning the visual cortex no longer responds to visual input
Hubel and Wiesel experiment proves the sensitive period
sutured monkey’s eye closed from 0-6 mo, animal was blind in that eye (cortical blindness)
Congenital cataracts prove the sensitive period
Congenital cataracts removed during infancy results in full vision
Cataracts removed between 10-20 resulted in the inability to perceive shape and form
Primary visual cortex
where information from two eyes first comes together; located in occipital lobe
Visual experience early in life determines
how much visual cortex is devoted to processing input (via neurons in the LGN) and degree to which inputs are combined
Layer 4 of the primary visual cortex
inputs from each eye cluster separately here, cells activated by each eye send input to common target cells above and below layer 4
target cells above and below layer 4 of the primary visual cortex receive input from
BOTH the right and left eye (SMALL proportion respond exclusively to 1 eye)
Binocular interaction
represented by the anatomical convergence on the same target
Visual experience during the sensitive period
results in competition among afferents from the LGN to layer 4; normally the eyes are used equally resulting in equal ocular dominance columns
Unequal balance between LGN afferents, due to vision impairments (monocular lid closure or cataracts) causes
impaired eye to lose the ability to drive layer 4 neurons in a large region of the cortex, LGN afferents from the normal eye GAIN ability to drive layer 4 neurons in a larger portion on the cortex
Result from impaired eye on functional properties
activity in the visual cortex becomes driven largely by LGN afferents from the normal eye
Axonal Architecture also changes if visual experience is withdrawn
axonal arbors of the LGN to layer 4 shrink in the impaired eye and expand in the normal eye
In cats, 1 week deprivation of visual stimuli before 6 mo of age results in
complete loss of vision; whereas deprivation in an adult has no effect
Critical period
period of maturation of cortical connections that is reliant on experience and stimuli
Closure of sensitive periods
once adequate experience is perceived, the circuit IRREVERSIBLY commits to a pattern of connectivity
Experience-driven sharpening of functional tuning
Major factor that decreases the plasticity of circuits; experience selects for anatomical connections and synaptic efficacy that refine excitatory and inhibitory connections, once this refining takes place it is difficult to alter via different experiences
Deprivation of appropriate experiences causes the sensitive period to be ________
prolonged
Raising cats in complete darkness would
prolong the critical period for ocular representation in the visual cortex
What event triggers sensitive period adjustments?
powerful and repeated activation of neurons at the site where change takes place
WIthout powerful and repeated stimuli
the pathway remains in an uncommitted state and capable of adjusting to experience
Therapeutic aspect of the critical period
Someone with abnormal sensory input, can be deprived of all relevant sensory input until the abnormality is corrected, resulting in a prolonged sensitive period rather than a commitment to an abnormal pattern of connectivity
Principles of developmental learning
Mainly regulated by genetic predisposition, limited range of stimuli can influence the circuit
Filial imprinting
a rapid discrete time segment in which animals display imprinting on the first stimuli they see
Babies in the process of imprinting
preferentially like images that resemble member of their own species
Sensitive periods exist for:
fundamental capacities (stereoscopic vision, visual acuity, binocular coordination) and high-level capacities (social behavior, language, perception of shapes and faces)
Language sensitive period
before 7 y/o a 1st or 2nd language results in thorough command of language; after 7 y/o the degree of proficiency decreases progressively (does not affect the ability to learn new words)
Language is processed in the ____ hemisphere
left “dominant”
If a 2nd language is learned before 7y/o the areas of the brain _________ with that of the 1st language. If a 2nd language is learned after 7 y/o the areas of the brain _________ with that of the 1st language
Overlap before 7y/o; do not overlap after 7y/o
Social behavior depends on social experiences at specific periods of neuronal development
Social deprivation in the early months of life result in developmental delays and hospitalism syndrome, by age 2-3 the development was still delayed suggesting structural deficits in brain development
Hospitalism syndrome
Rene Spitz’s term for infants that were raised in a hospital and lacked the appropriate social stimuli which went on to have retarded physical development, and disruption of perceptual-motor skills and language
Theory of Mirror Neurons Circuitry
Specific type of neuronal population in the frontal and parietal lobes (also in areas related to visions and memory) necessary for imitation learning, understanding of others’ mood and actions, identity and imitation of adults
Dysfunction of mirror neurons may lead to _____
autism and the inability to empathize
Mirror neurons are subject to critical periods
plasticity is minimal following critical period
Mirror neurons fire when
either the individual acts or when the same action done by another individual is perceived
